KETENES  , in

chemistry, a group of organic compounds which may be considered as internal anhydrides of acetic acid and its substitution derivatives . Two classes may be distinguished: the aldo-ketenes, including ketene itself, together with its mono-alkyl derivatives and carbon suboxide, and the keto-ketenes which .comprise the dialkyl ketenes . The aldo-ketenes are colourless compounds which are not capable of autoxidation, are polymerized by pyridine or quinoline, and are inert towards compounds containing the groupings C:N and C:0 . The ketoketenes are coloured compounds, which undergo autoxidation readily, form ketene bases on the addition of pyridine and quinoline, and yield addition compounds with substances containing the C:N and C:0 groupings . The ketenes are usually obtained by the action of zinc on ethereal or ethyl acetate solutions of halogen substituted acid chlorides or bromides . They are characterized by their additive reactions: combining with water to form acids, with alcohols to form esters, and with primary amines to form amides . Ketene, CH2:CO, was discovered by N . T . M . Wilsmore (Jour: Chem . Soc., 1907, vol . 91, p .

1938) among the gaseous products formed when a platinuth

wire is electrically heated under the surface of acetic anhydride . It is also obtained by the action of zinc on bromacetyl bromide (H . Staudinger, Ber . 1908, 41, p . 594) . At ordinary temperatures it is a gas, but it may be condensed to a liquid and finally solidified, the solid melting at -151° C . It is characterized by its penetrating smell . On standing for some time a brown-coloured liquid is obtained, from which a colourless liquid boiling at 126-127 C., has been isolated (Wilsmore, ibid., 1908, 93, p . 946) . Although originally described as acetylketen, it has proved to be a cyclic compound (Ber., 19o9, 42, p . 4908) . It is soluble in water, the solution showing an acid reaction, owing to the formation of aceto-acetic acid, and with alkalis it yields acetates .

It differs from the

simple ketenes in that it is apparently unacted upon by phenols and alcohols . Dimethyl ketene, (CH3)2C :CO, obtained by the action of zinc on a-brom-isobutyryl bromide, is a yellowish coloured liquid . At ordinary temperatures it rapidly polymerizes (probably to a tetramethylcylobutanedione) . It boils at 34° C . (75o mm.) (Staudinger, Ber . 1905, 38, p . 1735; 1908, 41, p . 2208) . Oxygen rapidly converts it into a white explosive solid . Diethyl ketene, (C2H3)2C :CO, is formed on heating diethylmalonic an-hydride (Staudinger, ibid.) . Diphenyl ketene, (C,H6)2C :CO, obtained by the action of zinc on diphenyl-chloracetyl chloride, is an orange-red liquid which boils at 146° C . (12 mm.) .

It does not polymerize .

Magnesium phenyl bromide gives triphenyl vinyl alcohol .